Solve 9x − 12 = −84

The solution of 9x − 12 = −84 is x = -8.

9x - 12 = -84\ \Rightarrow\ x = -8

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The lines y = 9x − 12 and y = -84 meet at x = -8. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$9x - 12 = -84$
2
Add 12 to both sides:
$9x - 12 + 12 = -84 + 12 \ \Rightarrow\ 9x = -72$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{-72}{9} \ \Rightarrow\ x = -8$
4
Check: put x = -8 back into the equation.
$9\cdot(-8) - 12 = -72 - 12 = -84 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 12 = -84\ \Rightarrow\ x = -8 \]
\[ 9x - 12 = -84 \]
\[ 9x - 12 + 12 = -84 + 12 \ \Rightarrow\ 9x = -72 \]
\[ \frac{9x}{9} = \frac{-72}{9} \ \Rightarrow\ x = -8 \]
\[ 9\cdot(-8) - 12 = -72 - 12 = -84 \checkmark \]

Trying values of x in 9x − 12 = −84

x	9x − 12	Equals -84?
-10	-102	no
-9	-93	no
-8	-84	yes
-7	-75	no
-6	-66	no

Questions

What is x in 9x − 12 = −84?

The solution of 9x − 12 = −84 is x = -8.

How do you solve 9x − 12 = −84?

Add 12 to both sides to get 9x = -72, then divide both sides by 9 to get x = -8.

How do I check the answer?

Replace x by -8: 9(-8) − 12 = -84, which is -84.

Solve 9x − 12 = −84

How to work it out

Trying values of x in 9x − 12 = −84

Questions

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